The main goal of this award is to further my career as a surgeon-scientist by establishing a successful research program. My longstanding interest in treating hearing disorders and, in parallel, performing basic science research on the same topic has fueled my decision to become a pediatric otolaryngologist-scientist. Since my clinical practice focuses on pediatric otology, I am frequently confronted with children suffering from hearing loss. As a physician, I have noticed a major deficiency in our current treatment approach where we cannot reverse sensorineural hearing loss. As a scientist, I hope to establish a research program that will shed light on therapies that restore hearing. To build on my previous research experience, this award is designed to help me develop into an independent investigator through hands-on training and close guidance on experimental designs, techniques, and grant writing. Because Wnt signaling plays major roles in maintaining stem cell populations in other organ systems, we hypothesize that canonical Wnt pathway is involved in the maintenance of cochlear progenitor/stem cells. Likewise, we hypothesize that loss of Wnt signaling or responsiveness is responsible for the inability of the mammalian cochlea to maintain regenerative capacity throughout life. Over the course of a five-year plan, we propose to conduct a series of experiments designed to test two unexplored hypotheses: 1) Wnt responsive cells are endogenous cochlear stem/progenitor cells, and 2) Wnt activation promotes proliferation in cochlear supporting cells. As single cells isolated via flow cytometry, different cochlear cell populations, including Wnt responsive cells and various cochlear supporting cells, are assessed for their ability to self-renew by sphere assays and their ability to generate new hair cells and supporting cells in vitro. Using markers for proliferation and cell lineage analysis in organotypic cultures, we will investigate the effects of Wnt agonists, mitogens, and neomycin-induced hair cell loss on these cells. At the end of this award, we will have evaluated and reported the roles of canonical Wnt signaling in regulating the endogenous Wnt responsive cells and cochlear supporting cells, and whether the Wnt pathway is a promising therapeutic target for hearing restoration. The long-term goal of our research is to maintain or activate a reserve of endogenous stem cells capable of restoring hearing and balance disorders through hair cell/supporting cell regeneration.